Microsoft announced at the Build conference today that Windows Azure now has 8.5 trillion objects stored on its infrastructure.

The company also announced the following:

Customers do 900,000 storage transactions per second.

The service is doubling its compute and storage every six months.

3.2 million organizations have Active Directory accounts with 68 million users.

More than 50 percent of the world’s Fortune 500 companies are using Windows Azure.

In comparison, Amazon Web Services said at its AWS Summit in New York earlier this year that its S3 storage service now holds more than 2 trillion objects. According to a post by Frederic Lardinois, that’s up from 1 trillion last June and 1.3 trillion in November, when the company last updated these numbers at its re:Invent conference.

So what accounts for the differene between Azure and AWS? It all has to do with how each company counts the objects it stores. With that in consideration, it’s likely Azure’s numbers are far different if the same metrics were used as AWS.

Nevertheless, the news highlights the importance of Windows Azure for Microsoft, especially as the enterprise moves its infrastructure, shedding data centers to consolidate and reduce their costs.